Reversible Thickness Engineering in Amorphous In<sub>2</sub>O<sub>3</sub> Transistors.

Pan, Yi-Yu; Hsu, Chu-Hsiu; Tseng, Robert; Wang, Sung-Tsun; Chang, Yu-Cheng; Chen, Shih-Chieh; Kimura, Takashi; Lan, Yann-Wen et al. · Nano Lett · 2026

basic_science · Level V

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Abstract

Amorphous oxide semiconductors offer a unique platform for versatile device processing, as their noncrystalline nature eliminates the requirement for lattice matching at the interface and enables low-temperature regrowth and isotropic processing. Leveraging chemical continuity of amorphous surface, this study demonstrates atomic-scale, reversible thickness control of amorphous In<sub>2</sub>O<sub>3</sub> by integrating bottom-up atomic layer deposition with top-down hydroxide-assisted wet-etching processes. The processes achieve bidirectional modulation of the film thickness from 1 to 4 nm under back-end-of-line compatible conditions while maintaining smooth surfaces (<i>R</i><sub>a</sub> = ∼0.5 nm) and stable chemical composition. This thinning-regrowth process enables precise, thickness-dependent control over the In<sub>2</sub>O<sub>3</sub> transistor performance, facilitating doping-free modulation of the threshold voltage and reversible switching between depletion- and enhancement-mode operation within a single device. Successful demonstration of inverters and ring oscillators confirms the robustness of this technique, establishing film thickness as a core design parameter for oxide semiconductors and paving the way for reconfigurable electronics.